1. Field of the Invention
The present invention relates to a CMOS image sensor and a method of fabricating the same, and more particularly, to a CMOS image sensor in which light shielding layers are formed between microlenses to improve reflection characteristics and to protect the microlenses upon packaging, and a method of fabricating the same.
2. Discussion of the Related Art
Generally, an image sensor is a semiconductor device that converts an optical image to an electric signal. In a CCD (charge coupled device) image sensor, a plurality of MOS (metal-oxide-metal) capacitors are arranged close to one another to transfer and store electric charge carriers. In a CMOS (complementary MOS) image sensor, a plurality of MOS transistors corresponding to the number of pixels are fabricated by CMOS technology. CMOS image sensors also typically include a control circuit and a signal processing circuit as peripheral circuits and a switching system that detects outputs of photosensors such as photodiodes step by step using the MOS transistors.
Hereinafter, a CMOS image sensor and a method of fabricating the same according to the related art will be described in detail with reference to FIG. 1 of the attached drawings, which shows a cross-sectional view illustrating a CMOS image sensor according to the related art.
A plurality of photodiodes 11 are formed on a semiconductor substrate 10, and first insulating layers 12 and metal lines 13 are alternately formed on the semiconductor substrate 10 including the photodiodes 11 in plural. (For clarity, interfaces between adjacent insulator layers in the first insulating layers 12 are not shown.) Then, a second insulating layer 14 including an oxide layer is formed on the first insulating layer 12 and planarized. A light shielding material is formed and patterned on the second insulating layer 14 to form a patterned light shielding layer 15. Then, in order to protect the patterned light shielding layer 15, a third insulating layer 16 (e.g., an oxide layer or a nitride layer) is formed on the light shielding layer 15 and planarized. The planarization typically uses a chemical mechanical polishing (CMP) method. Then, microlenses 17 are formed on the third insulating layer 16 between the light shielding layers 15. As shown in FIG. 1, the microlenses 17 partially overlap the ends of the light shielding layers 15.
The CMOS image sensor and the method of fabricating the same according to the related art have the following problems. In the case of using the light shielding layer, since the method forms a planarized insulating layer for protecting the light shielding layer and for providing a planar surface for subsequent formation of microlenses, the number of steps increases and thus manufacturing efficiency decreases. Also, since the packaging process is performed after the microlenses are formed (and, in some cases, while the microlenses are exposed), protecting the microlenses during packaging can be difficult and/or unnecessarily complex.